Temperature control system



June 17, 1941.

A. C. GRANT TEMPERATURECONTROL SYSTEM Filed Dec. 7, 1938 inventorPatented June 17, 1941 TEMPERATURE CONTROL SYSTEM Arthur C. Grant, St.Paul, Minn., assignor to Minneapolis-Honeywell Regulator Company,Minneapolis, Minn., a corporation of Delaware Application December 7,1938, Serial 'No. 244,405

12 Claims.

The present invention relates to a temperature control system and moreparticularly to one in which the flow of temperature changing fluid to atemperature changing device is modulated in accordance with acontrolling condition.

An object of the present invention is to provide a temperaturecontrolling system employing a temperature changing means supplied witha temperature changing fluid wherein a valve controls the supply oftemperature changing fluid to said temperature changing means, the valvebeing modulated by an actuator in accordance with a desired controllingcondition and wherein there is an electromagnetic connection between theactuator and the valve, which electromagnetic connection is releasedupon the temperature of the space whose temperature is being controlledassuming a predetermined value.

A further object of the present invention is to provide such a systemwherein the electromag- 1 netic means is also deenergized when the valvereaches a position so close to a predetermined one as to prevent properoperation of the temperature changing means. r

A further object of the present invention is to provide such a system inwhich the temperature changing device is a heating means and in whichthe electromagnetic connection is deenergized when the temperature inthe space being heated rises above a-predetermined value.

A further object of this present invention is to provide such a controlsystem in connection with a heating system employing a fluid medium fortransferring the heat from the heating means to the space being heated,and wherein the valve is modulated in accordance with the temperature ofthis fluid medium.

A further object of the present invention is to provide a system such asset forth in the preceding object in which the valve is modulated inaccordance with the temperature of the fluid medium returning from thespace to the heating means.

A still further object of the present invention is to provide such asystem in connection with a gas burning furnace wherein means areprovided for releasing the electromagnetic connection when the valvereaches a position such that when the flow of gas therethrough isincapable of maintaining proper combustion.

Other objects of the invention will be apparent from a consideration ofthe accompanying specification, claims, and drawing.

In the single figure of the drawing, the temperature control system ofthe present invention is shown in schematic form with the valve portionthereof shown in larger scale than the rest of the elements of thesystem in order to more clearly indicate the details of constructionthereof.

Referring to the drawing, a warm air furnace is generally designated bythe reference numeral It. This furnace comprises a furnace properdesignated by the reference numeral III which is surrounded by a jacketl2. Located within the furnace proper is a gas burner I3 and a normallyconstantly burning pilot burner M. The air which is to be heated entersthe furnace at a cold air inlet l5 and passes inside of the casing 12out to a hot air delivery pipe Hi. The delivery pipe I6 is provided withvarious branch ducts ll (only one of which is shown), each of whichducts leads to a register l8 in a space I!) which is to be heated. Alsolocated in the space I9 adjacent the floor is a'return air registerconnected with a return air branch pipe 2|, which in turn connects withthe main return air duct 22. This a return air duct 22 is connected tothe furnace at the cold air inlet l5.

The main burner I3 is supplied with gas by a pipe 25 connected to a gassupply pipe 26, the connection being controlled by a valve 21. The gasbefore entering the burner passes through a mixing chamber 24 ofconventional type, in

tending through the aperture of the partition wall in sliding engagementwith the wall of the aperture. The sleeve 8 is provided with theconventional inverted V shaped slots 9 to provide a uniform variation inflow with change in the valve position. Secured to the valve disc 32 byany suitable fastening means is a valve stem 33. A diaphragm 34 isclamped between two washers 35 and.33 by nuts 31 and 38 which arethreadedly engaged with the valve stem 33. The outer edge 'of thediaphragm is clamped between the valve casing 21 and a circular plate 39which is aperhired at 40 to permit the valve stem 33 to extend upwardlytherethrough. Supported upon the plate 39 is an inverted cup shapedcasing 42. Secured to the top of this casing is a smaller cup shapedcasing 43 in which is located a bellows element 45. Enclosing thecasings 42 and 43 is an outer casing member 44. Connected to theinterior of the casing 43 and extending through casing 43 and casing 44is a capillary tube 41 which leads to a bulb 46 located in the returnair duct 22. The bulb 46 is filled with a suitable volatile fluid andthe pressure .of vaporization of this fluid is transmitted to theinterior of the housing 43 and consequently to bellows 45.

The bulb and bellows construction J'ust described forms the actuator forthe valve, which actuator is employed to modulate the valve inaccordance with return air temperature. An electromagnetic connection isprovided between the valve and this actuator. Secured to the under sideof the upper wall bellows 45 is a plunger 48. This plunger is adapted tobear against a core member 49 of magnetic material which is providedwith a number of downwardly extending portions to provide a generallyinverted cup shaped configuration. Wound upon the core member 49 is anelectromagnetic winding 50. operating with the armature 49 is a core 5|which is longitudinally movable in the cylindrical recess of winding 58.A spring 53 serves to bias the coil and armature construction intoengagement with the plunger 48. Upon energization of the winding 50, thesolenoid core is drawn up into engagement with the armature 49 and isthereafter movable therewith. Upon the return air temperature rising,the pressure exerted on bellows 45 is increased and the entire assemblycomprising plunger 48, core member 49, solenoid core 5|, and valve disc32 is moved downwardly towards valve closed position.

Secured to core member 49 is a switch blade 55 which is adapted tocooperate with an adjustable contact 56 extending through an insulatedblock 51 secured in the casing 42. The contact 56 is at the end of ascrew 58 so that upon threading the screw in or out, the spacing of thecontact from the switch blade 55 may be adjusted.

Provisionis made for securing modulating operation of the valve duringpower failure. Secured to the lower side of valve disc 32 is a rod 11which carries an inverted cup-shaped member 18 telescopingly engaging asecond cup-shaped member 19 carried by a screw 80. The two cupshapedmembers 18 and 19 act as guides for a spring 8| supported by the lowercup-shaped member 19. The spring 8| is of limited extensibility and withthe screw 80 in the position shown, which is the position for normaloperation, the spring 8| does not engage the upper wall of cupshapedmember 18. If it is desired to operate the system during a powerfailure, the screw 80 may be screwed inwardly until the screw head 83engages a boss 84 of the valve casing. Inthis position, the spring willexert enough force upon the solenoid core 5| to hold it in engagementwith the core member 49 even when core member 49 is in its uppermostposition.

A thermostat 59 is located in the space l9. This thermostat may be ofany suitable construction but is shown for purposes of illustration ascomprising a bimetallic element 60 to which is and contact breakingoperations of the thermostat. This differential eliminates thedisadvantage of the thermostat opening and closing its circuit anexcessive number of times when thrla temperature is at approximately thedesired va 1.18.

A further thermostatic switch is designated by the reference numeral 65.This thermostatic switch corn-prises a helical bimetallic element 66which extends into the bonnet of the furnace Ill and which has the endthereof connected to a rod 61 which, in turn, is connected to a switchblade 68. Switch blade 68 is adapted to be moved into and out ofengagement with a fixed contact 69. The bimetal element upon beingheated servesto rotate rod 61 and consequently switch blade 68 in aclockwise direction. The thermostatic switch 65 is employed as a limitcontrol responsive to bonnet temperature.

Operation The various elements of the system are shown in the positionwhich they assume when the room thermostat is calling for heat but inwhich the valve has been modulated so nearly to closed position that theswitch consisting of switch blade 55 and contact 56 has been opened tocause deenergization of the winding 58. This deenergization of thewinding 56 has resuted in valve 32 being moved to closed position byreason of the bias imparted by its own weight and the weight of solenoidcore 5|. Particularly in the case'of a gas burner, it is undesirable tocontinue operation of the burner after the fluid supplied thereto hasreached a predetermined minimum. If the gas supplied is reduced belowthis minimum, the pressure of the gas will be insufilcient to maintainthe flame at the burner so that combustion will take place in the mixer24.

Let it .be assumed 'now that the temperature of the return air falls toa point such that switch blade 55 is moved into engagement with contact56. An energizing circuit will then be established to the winding 50 asfollows: from conductor 10 through switch blade 68, contact 69,conductor 1|, contact 62, contact blade .6|-, bimetal 60, conductor 13,contact 56, switchblade 55, conductor 14, winding 59, and conductor 15.It will be understood that conductors 19 and 15 lead to any suitable.source ofpower (not shown). The establishment of the circuit just tracedresults in solenoid core 5| being abruptly moved upwardly.

into engagement with core member 49. The contakes place is such thatwhen the core moves upwardly into engagement with the member 49, thevalve will pass sufllcient fluid to the gas burner to properly supportcombustion. It is to be understood, of course, that whenever the valveis throttled towards closed position to a point that switch blade 55separates from contact 56, the above traced circuit will beinterruptedwith the result that the valve moves to closed position asshown in the drawing.

The thermostat 59 will normally be set at a temperature slightly abovethe optimum temperature. In view of'the fact that the return While the 4modulation of the valve in accordance with the return air temperature isshown, it is to be understood that the valve could be modulated inaccordance with other conditions indicative of the heat loss from thespace l9. Thus the valve might well be modulated in accordance withbaseboard temperature or even outdoor temperature. In fact, certainfeatures of the invention are applicable to modulation of the valve fromany desired condition indicative of the demand for burner operation suchas bonnet temperature or, in the case of a hot water boiler, boilertemperature. While the valve is normally maintained in such a positionthat the right amount of fuel is supplied to the gas burner, it ispreferable to insure that if the gas flow is not quite proper, it besupplied in excess of that required in order to insure that an adequateamount of fuel will be supplied to properly heat the space l9. For thisreason, continued operation of the gas burner may eventually produce acondition wherein the space temperature rises to the point slightlyabove that desired at which thermo-- stat 59 is set to operate. Whenthis point is reached, the thermostat opens its contacts and deenergizesthe winding 50. Such deenergization of the winding 50 will cause valve32 to abruptly move to closed position. Thus, with 'JhiS arrangement,the valve is normally modulated to supply heat at a rate equivalent toor slightly above the rate necessary to maintain the space temperatureat the desired point and whenever the space temperature does rise:lightly above the desiredvalue, the operation of the burner is abruptlyterminated until the space temperature again falls to such value.

It will be noted that the original energizing circuit in addition toincluding the thermostat 59 and the switch comprising switch blade 55and contact 56 also included the thermostatic switch 65. This switch isnormally maintained closed and is opened only when the bonnettemperature rises to an excessively high point such as may occur duringa morning pick-up period or in the case of an extremely suddentemperature drop, such as occasioned by the demand for the heating ofrooms not normally heated. In such case, the opening of this switchcomprising switch blade 68 and contact 69 will deenergize the winding 50to cause valve 32 to abruptly move to closed position.

In the event of power failure, the screw 80 is screwed inwardly untilthe screw head 83 engages the boss 84. In this position of the screw 80,the spring 8| is efiective to urge the core against the core member 49regardless of the position of the latter ihember. The'valve is then freeto be modulated in accordance with return air temperature, themodulation being effected against the action of both springs 53 and 8|.Due to the fact that spring Bl exerts a relatively small force comparedwith spring 53, the valve will assume substantially the same positionfor a given return air temperature as when the core 5| is held inengagement with the core member 49 by reason of the energization of coil'50.

It will be seen that I have provided a system wherein the supply oftemperature changing fluid to a temperature changing device is modulatedin accordance with the demand for operation of, the temperature changingdevice and wherein upon the space temperature rising above a desiredvalue, upon the valve being movedto a position too close to closedposition to properly sustain operation of the temperature changingmeans, or when the temperature adjacent the temperature changing meansrises to an excessively high value, the valve is moved to closedposition. This, moreover, is accomplished by means of an extremelysimple valve mechanism having a minimum number of parts.

While I have shown a specific embodiment of the invention for purposesof illustration, it ,is to be understood that the invention is limitedonly by the scope of the appendedclaims.

I claim as my invention:

1. In a temperature control system, temperature changing means, meansfor supplying a temperature changing fluid to saidtemperature changingmeans, a valve biased to a predetermined position and controlling theflow of such temperature changing fluid to said temperature changingmeans, an actuator for said valve, means responsive to a conditioninfluenced by the heat transfer between a room whose temperature isbeing controlled and the outdoors for causing said actuator to modulatesaid valve in accordance with the value of said condition, anelectromagnet connection between said actuator and ,said valvecomprising an electromagnet and armature one of which is connected tosaid valve and the other of which is positioned by said actuator, andmeans for deenergizing said electromagnet to release said valve to saidpredetermined position. when the room temperature assumes apredetermined value.

2. In a temperature control system, temperature changing means, meansfor supplying a temperature changing fluid to said temperature changingmeans, a valve biased to closed position and controlling the now of suchtemperature changing fluid to said temperature chang ing means, anactuator for said valve, means responsive .to a condition indicative ofthe demand for operation of said temperature changing means for causingsaid actuator to modulate said valve in accordance with the value ofsaid condition, an electromagnetic connection beture changing means,means for supplying a temperature changing fluid to said temperaturechanging means, a valve biased to a predetermined position andcontrolling, the flow of such temperature changing fluid to saidtemperature changing means, an actuator for said valve, means responsiveto a condition influenced by the heat transfer between a room,whosetemperature is being controlled and the outdoors for causing saidactuator to modulate said valve in accordance with the value of saidcondition, an electromagnetic connection between said actu ator and saidvalve comprising an electromagnet and armature one of which is connectedto said valve and the other ofiwhich is positioned by said actuator, andmeans for deenergizing said electromagnet to release said valve to saiddetermined position when the room temperature assumes a predeterminedvalue or when the position to which said valve would be moved by saidactuator would be too near to said predetermined position to operate thetemperature changing means properly.

4. In a temperature control system, means for heating a fluid medium,means for conveyin the fluid medium from the heating means into heattransferring relation with a room to be heated and back to said heatingmeans, means for supplying a heat producing fluid to said heating means,a valve biased to closed position and controlling the flow of said heatproducing fluid to said heating means, an actuator for said valve, meansresponsive to the temperature of said fluid medium for causing saidactuator to modulate said valve in accordance with said temperature, anelectromagnetic connection between said actuator and said valvecomprising an electromagnet and armature one of which is connected tosaid valve and the other of which is positioned by said actuator, andmeans for deenergizing said electromagnet to release said valve toclosed position when the room temperature rises above a predeterminedvalue.

5. In a temperature control system, means for heating a fluid medium,means for conveying the fluid medium from the heating means into heattransferring relation with a room to be heated and back to said heatingmeans, means for supplying a heat producing fluid to said heating means,a valve biased to closed position and controlling the flow of said heatproducing fluid to said heating means, an actuator for said valve, meansresponsive to the temperature of the fluid medium returning to saidheating means for causing said actuator to modulate said valve inaccordance with said temperature, an electromagnetic connection betweensaid actuator and said valve comprising an electromagnet and armatureone of which is connected to said valve and the other of which ispositioned by said actuator, and means for deenergizing saidelectromagnet to release said valve to closed position when the roomtemperature rises above a predetermined value.

6. In a temperature control system, heatin means including a gas burner,means for supplying gas to said burner, a valve biased to closedposition and controlling the flow of gas to said burner, an actuator forsaid valve, means responsive to a condition indicative of the demand forheat for causing said actuator to modulate said valve in accordance withthe value of said condition, an electromagnetic connection between saidactuator and said valve comprising an electromagnet and armature one ofwhich is connected to said valve and the other of which is positioned bysaid actuator, and means for deenergizing said electromagneticconnection to 3 release said valve to closed position when the positionto which said valve would be moved by said actuator would be too near toclosed position to permit a flow of gas sufiicient to support combustionproperly.

7. In a temperature control system, a warm air furnace including a fluidfuel burner, means for conveying-the heated air to a room bein heatedand for returning the air to the furnace, means for supplying fluid fuelto said burner, an actuator for said valve, means responsive to thetemperature of the air returning from the room for causing said actuatorto modulate said valve in accordance with said temperature, anelectromagnetic connection between said actuator and said valvecomprising an electromagnet and armature one of which is connected tosaid valve and the other of which is positioned by said actuator, andmeans for deenergizing said electromagnetic connection to release saidvalve to closed position when the room temperature rises above apredetermined value.

8. In a temperature control system, temperature changing means, meansfor supplying a temperature changing fluid to said temperature changingmeans, a valve biased to a predetermined position and controlling theflow of such temperature changing fluid to said temperature changingmeans, an actuator for said valve, means responsive to a conditioninfluenced by the heat transfer between a room whose temperature isbeing controlled and the exterior thereof for causing said actuator tomodulate said valve in accordance with the value of said condition, areleasable connection between said actuator and said valve forpositively connecting said members together, and means for effecting arelease of said connection to release said valve to said predeterminedposition when the room temperature assumes a predetermined value.

9. In a temperature control system-temperature changing means, means forsupplying a temperature changing fluid to said temperature changingmeans, a valve biased to closed position and controlling the flow ofsuch tempera-' ture changing fluid to said temperature changing means,an actuator for said valve, means responsive to a condition. influencedby the heat transfer between the space whose temperature is beingcontrolled and the exterior thereof for causing said actuator tomodulate said valve in accordance with the value of said condition, areleasable connection between said actuator and said valve forpositively connecting said members together, and means for effecting arelease of said connection to releasesaid valve to closed position whenthe position to which said valve would be moved by said actuator wouldbe too near to closed position to operate the temperature changing meansproperly.

10. In a temperature control system, temperature changing means, meansfor supplying a temperature changing fluid to said temperature changingmeans, a valve biased to a predetermined position and controlling theflow of such temperature changing fluid to said temperature changingmeans, a mechanical actuator for said valve, means responsive to a firstcontrolling condition for causing said actuator to modulate said valvein accordance with the value of said condition, electromagneticconnecting means between said actuator andsaid valve for positivelyconnecting said members together, a source of electrical energy, meansincluding a switch re-i sponsive to a second condition for electricallyconnecting said electromagnetic connecting means to said source ofelectrical energy, and

means for mechanically maintaining said connection between said actuatorand valve in the event of the failure of said source of electricalenergy.

11-. In a temperature control system, temperature changing means, meansfor supplying a -temperature changing fluid to said temperature changingmeans, a valve biased to a predetermined position and controlling theflow of such temperature changing fluid to said temperature changingmeans, a. non-electric actuator for said valve, means responsive to afirst controlling condition for causing said actuator to modulate saidvalve in accordance with the value of said condition, electromagneticconnecting means between said actuator and said valve, a source ofelectrical energy. means including a switch responsive to a secondcondition for electrically connecting said electromagnetic 'connectingmeans to said source of electrical energy. and means for applying tosaid valve a force not normally applied thereto for biasing the sameinto operative connection with said actuator in the event 01' thefailure of said source of electrical energy.

12. In a temperature control system, means for heating a fluid medium,means for conveying the fluid medium from the heating means into heattransferring relation with a space to be heated and back to said heatingmeans. means for supplying a heat producing fluid to said heating means,a valve biased to closed position and controlling the flow of said heatproducing fluid to said heating means, an actuator for said valve, meansresponsive to the temperature or said fluid medium for causing saidactuator to modulate said valve in accordance with said temperature. anelectromagnetic connection between said actuator and said valvecomprising an electromagnet and armature one or which is connected tosaid valve and the other of which is positioned by said actuator, andmeans for deenergising said electromagnet to release said valve toclosed position when the position to which said valve would be moved. bysaid actuator would be too near to closed position to operate-theheating means properly.

ARTHUR 0. GRANT.

